Dehydrating method and apparatus



April 36 w45 w. A. PATRICK, JR., ET AL DEHYDRAT'ING METHOD AND APPARATUS Filed June 27, 1942 4 Sheets-Sheet l April 30, 1946. w. A. PATRICK, JR., ETAL 2,399,246

DEHYDRATING METHOD AND APPARATUS Filed June 2'7. 1942 4 Sheets-Sheet 2' Aprrl 3Q, 1946. w. A. PATRICK, JR., ETAL 2,399,246

DEHYDRATING METHOD AND APPARATUS Filed June '27, 1942 4 sheets-sheet 5 @aya April 30, 1946. w. A. PATRICK, JR., ET AL A 2,399,245

DEHYDRATING METHOD AND APPARATUS Filed June 27, 1942 4 Sheets-Sheet 4 Patented Apr. 30, 19,46

STATES Para r F'FCE` DEHYDRATIN G METHOD AND APPARATUS Application June 27, 1942, Serial No. 448,875

(Cl. S-49) 13 Claims.

This invention relates to method and apparatus for` dehydrating, or concentrating, any material required to be so treated, for example, biological products such as serums, vaccines, etc., and foods such as eggs, fruit juices, etc. The principal object of the invention is to provide a sysu tem whereby the materials may be emciently and relatively rapidly and inexpensively reduced to i mercial operations.

According to the present invention, we form a film of the material to be treated and subject this lm to redt ed pressure to promote evaporation, while preferably maintaining in the evaporation zone an above freezing temperature. While such a lin may be formed in various Ways, we

prefer to form it continuously on an endless 'sur-b face whereon the`iilm is continuously renewed. As will be described in detail hereinafter, this may be simply done by placinga` batch ofl the material in the lower portion of a rotary drum, or by immersing the lower external portion of a rotary, drum in a. batch of the material.

L In the use of desiccants in the nature of sorpti've agents such as silica gel, Activated Alumina,

etc., the temperature of the desiccant is raised jas a result of the condensation thereby of the tion of illustrative apparatus as shown in the accompanying drawings, in4 which:

Figure 1 is a view, partly in section and partly in elevation, of one form of suitable apparatus; Figure 2 is a section substantially on line 2 2 of Figure 3;

Figure 3 is a view taken at right angles to that of Figure 1, with further parts in section;

Figure 4 is a section on line llid of Figure 3; Figure 5 shows in perspective an end plate, trunnion, and baiile unit which appears in Figure 3;

Figure 6 shows in axial section another embodiment of the invention;

Figure '7 is a section on line l-l of Figure 6, and

Figure 8 is a section on line 8--8 of Figure 6. Referring to the drawings, and first to Figures 1 to 5, reference numeral l5 designates a base plate having a top annular shoulder to which is xed a sealing gasket i6 on which is adapted to rest the lower edge of a glass bell ll, as here shown. The base plate and the bell constitute a vacuum chamber with a suction connection la leading from the bottom center ofthe base plate.

Uprights I 9 and 2li mounted on the base plate have at their upper ends horizontal bearing portions in which are journaled hollow or tubular trunnions 2| and 22 which are xed centrally of4 circular end plates 23 and 2d, thel end plates constituting'portions of a drum generally indicated by the reference numeral 25. Bailie devices 2t and water vapor derived from the drying substance.

` The term sorb is used herein as covering the phenomena of adsorption and absorption, that is to say, the idea of mechanical condensation in general. Where the desiccant is in the nature of a'chemical with which the Water vapor will react to form a hydrate, there is a resultant heat of g reaction. The term desiccant as used herein ifdenotes any substance which will take up evolved vapor either by sorption or chemically with a`I 'consequent generation of heat, and the present invention preferably involves theuse of such a desiccant disposed in heat transferring relation to the film-carrying surface vso that the heat, or a portion of it, of the desiccant is transferred to the evaporating zone with,v the result thatthe desiccant is automatically maintained at an emr 2l project inwardly from the trunnions 2l and 22, respectively, and the structure o f the device 2l is shown in detail in Figures 3, 4, and 5. It comprises an open-ended hollow body formed of similar frusta 2-8 and 29 with their large ends joined together, radial openings being formed on the line of juncture. Portion 29 includes a sleeve 3| tightly received in an annular internal venlargement of trunnion 22. A circular plate or disc 32 is positioned within the internal enlargement defined by the frusta inwardly of the open end 33, and isof greater diameter or areathan the opening 33 so as to block any direct passage from the said opening to the trunnion. However, the area of the annular space between the disc and the walls of portion 28 is at least as great as the area of opening 33 so that while flow through the latter will be deected, the ow capacity is not aiected.

Drum 25 includes a cylindrical shell 3i whose ends are fixed to and secured against intermediate portions of annular plates 35 and 36, end plate 23 overlapping and being secured to the I ragainst shell I4. The latter and ilns 3l are of metal having good heat conductivity, for example, copper. and the ilus are secured to the shell, as

` by soldering, in order to establish good thermal contact. The desiccant is held in place by a cylinder 38 of wire mesh whose ends are fixed to the peripheries of plates l5 and 38. d

Reference numeral I0 designates a plug for a iilling-and emptying opening formed in plate 35 just inwardly of the inner surface of shell 34, and reference numeral 4I designates a liquid level indicator operatively associated with plate 35 for the purpose'of indicating the leveloi liquid inl the bottomportion of the drum. y

`Reference numeral 42 designates an electric motor with supply leads passing through and sealed in openings in base plate i5. IA sprocket on the motor'shaft drives, through chain 43, a

sprocket fixed on a counter shaft journaled in frames i9 and 2l, and a further sprocket on shaft u drives a sprocket l5, iixed on trunnion 2i, through chain II, whereby to rotate the drum IB With the drum in the position shown in Figures 1 and 3, and bell I1 removed, the material to be treated is introduced into the drum through the illling opening to the proper level as shown by the vindicator 4I. Plug 4I being replaced, the motor and the vacuum producing means are started. The vacuum producing means can be an ordinary vacuum pump, but since high vacuum is not re quired in theoperation of the apparatus, a small capacity steam iet evacuator is preferably used.

As the drum is rotated, the inner surface or shell u carries on it a film from the batch in the bottom of the drum, which nlm, as the drum rotates, is continuously returned to the batch and renewed, beingsubiected to thejlow pressure communicatedtol-theinterior oi' the drum through the hollow trunnions. Due to the large area of exposed film, evaporation is greatly accelerated. The evolved -Veppr'ffpass around the exterior of 'the drum and into'f-thedesiccantdisposed in that part of the suction' orvacuum line defined between the bell l1 and-shell 34, so-as to-be morel or less completely takenup, with a consequent generation oi' heat: This'heat, or part of it, is transferred by the desiccant and the iins 31 to the shell Il; The capacity lof the desiccantin relation to the evaporating capacity of the drum is such that .an above freezing temperature is maintained in the drum: and th'ezheat abstraction from the desiccant is suchas to maintain the latter at an emcient, substantially constant, operating temperature. The capacity of the desiccant for the purpose of maintaining the material being dehydrated at an above-freezing temperature is determined by several factors; for example, when Silica gel is `used the factors include the area orgel sur- -face exposed to the heat conducting surfaces, in-

- eventual insulation to an undesirable extent, but

vthis wetting also increases the exposed 'area of the material and takes advantage of the principle that evaporation is directly proportionate to the exposed area. lThe speed of rotation oi the 'lrum is not critical and it is only necessary that it .be suiicient to keep the interior walls at all times wet. l

The purpose of the baillesis to prevent liquid which tends to splash up from being discharged. The splash strikes the baille plates as at 32 and drains back to the drum interior through the holes, as at 30. Theconstruction is such that there is no increase in the velocity of the vapors as they pass through the balde chamberwlncrease in velocity would tend to cause` the vapors to entrain liquid and consequently,l as above pointed out, the area around the baille plates is at least equal to the area ofthe openings as at 32. The fins are perforated in order to permit an equalization of the vapor pressure throughout the entire body of the desiccant. Maximum efilciency can be obtained only when the desiccant is of substantially uniform effectiveness throughout. The fins serve to improve the heat transmission by collecting the heat quickly and transferring Ait directly to the shell 34. In their absence, heat from the outer zones of the desiccant would have to pass through the inner zones in-order to reach the drum wall, and silica gel, for example, is of low thermal conductivity.

Inasmuch as the drum of the described apparatus can be readily illled and emptied only through the opening normally closed by the plug 40, the dehydrating or concentrating operation will not be carried beyond a point at which the material is still. fluid enough to ybe drained through the opening, which 4opening can, of course, be made oi larger size ythan that indicated,

if desired.y With a larger' opening', the material can be pre-frozen and introduced into the drum in lumps in this condition.

hydrating operation may be preceded by a degassing operation with the material in initially frozen condition. 0f course, the thawing proc- -ess would begin almost immediately where a desiccant like silica gel is used, since heat would immediately start to develop as a result of the adsorption of the gases. The pre-frozen material-quickly becomes liquid so as to be spread as a illmon surfaces of the drum.

A particular application oi' the described apparatus is in the dehydration` of animal blood,

serum in the manufacture-of adhesive for unit-Y ing the cushion discs of crown caps to the metal shells. For this purpose, a serum having 46.64%

lsolids is desired, whereas blood serum usually has j tial salt content or approximately 1%.

If further dehydration is desired, apparatus such as is shown in Figures 6to 8 may be used, although it will be understood that the apparatus shown in these ilgures is equally well utilizable in dehydrating material from original condition.

Referring to these figures, reference numeral 50' designates a base to which are fixed uprights Si and 52 having at their upper ends bearings Entrained gases are quickly removed by suction whenv the material in frozen condition, and consequently the desecured and sealed annular end plates B and 51. Perforated annular fins 58 are secured within the shell 55 in good thermal contact therewith and a mass@ of desicc'ant is packed between the hns and against the inner surface of the shell,

being retained by a wire mesh cylinder 60.

The drum thus constituted, and indicated as a whole by the reference numeralv BI, is disposed within an outer chamber in the form of a cylindrical drum 62 which includes a cylindrical shell 63 and end walls 64 and 65. Brackets 66 and 61, rising from the pedestals 5l and 52, are secured to the end walls. Sti and 65 for the support of drum B2. These end walls are perforated for the passage of shaft 53 and wall Bd'carries packing means 68 so that a fluid-tight joint is formed between the wall and the shaft. Wall t5 has a central opening registering with the opening of end plate 5l of drum 6|, and xed to one or the other of these elements is an annular gasket 69 which forms an air-tight joint between them. Wall 65 has a horizontally projecting neck 70 which carries at its outer end l packing means li forming a fluid-tight joint with shaft 53, the neck 'lll being provided with a nipple to which is connected a hose l2 leading to any suitable vacuum producing means. At its lower part the drum is split in a horizontal plane,

and the two'parts are flanged and adapted to be secured together, through the intermediary of asealing gasket, by any readily releasable means.`

The lower portion A62a of the drum is equipped with a liquid level indicating device 153. v.The end plate 5t of drum 6l has fixed thereto around its opening a .series of concentric outwardly flared baiiie plates M, and theseare interleaved y with similar baille plates 'I5 fixedon 'endlwall Sli, the interleaved bailles beingfoiitofjontact with eachother to provide a tortuousrpassage from the outside of drum 6| to its interior.

Shaft 53 has fixed thereon a sprocket 16 adapted to be driven from any suitable source of power through a chain 11.

In the operation of this apparatus, drum portion 62a, which constitutes a pan, is dropped, or removed, and filled to a suitable level with the material to be treated, being then replaced in fposition. The drum is now rotated in. the direction of the arrow, Figure 7, and the vacuum producing means set in operation. The lower portion of drum ti being immersed-in the material, as shown in Figures 6 and 7, carries therefrom a film of the material as the drum is rotated, this nlm being returned to the batch and continuously renewed. The film is subjected to the vacuum induced through tube 12 and the drum interior, and the desiccant being, as beforeI interposed in the suction line, the ,vapor passing through the drum is more or less taken up, and the same heat transfer, as before, occurs. A

Inasmuch as the machine of Figure 6 to 8 is intended to be able to carry out -the dehydrating process to such an extent as to give a substantially solid product, toward the end of the operation it is necessary to provide means for scraping^the solidifyingfilm from the surfaces of drum Si. For this purpose, we pivot a shaft 18 in the end walls St and 65 in the annular space between the two drums, as particularly shownin Figures '7 and 8, this shaft having fixed thereto a scraper or doctor 19, which may be adjusted by means asada in which is Journaled a horizontal smit sa.

of an external handle et between operative and inoperative positions. In'Figures 7 and 8, the Y.

weight of handled@ holds the scraper aga-inst the drum periphery. When the handle is swung to the right beyond the vertical, its weight will hold the scraper away from the drum. VInasmuch as the outer marginal portions of plates 66 and 61 will also collect films, Scrapers for these portions as at tl, Figure 8, are "provided, these being mountedv on square shafts slidable in packings carried by the end walls d and S5, the scrapers being preferably spring pressed into engagement with the drum ends but retainable in retracted relation by any suitable means.

The bame elements it and l5 prevent splash from reaching the desiccant and from being carried out with. the vapor.

When the dehydrating step has been completed, the pan tia is ag'ain detached and its contents removed.

The same general remarks as to features of op` eration apply to the second embodiment as to the first.

It will be understood that the disclosed apparatus has been given only by way of example, and that the invention extends to all procedures and apparatus coming within the terms of the following claims.

We claim: f

l. The method of dehydrating which comprises continuously passing a portion of an endless trav-k eling member into a batch of the material to be dehydrated whereby a iilm of the material is withdrawn from the batch on said member and is returned to the batch, subjecting the lm to 2. The method of dehydrating which comprises' d@ immersing in a batch of the material to be dehydrated a lower portion of an endless member traveling in an orbit about a horizontal axis, whereby to cause the unimmersed portion of said member to carry a film of the material, subjecting the film to reduced pressure to promote evaporation, and passing the evolved vapors into a desiccant which is-in heat exchanging relation with said film.

3. Dehydrating apparatus comprising a chamber, a drum rotatable in said chamber on a horizontal axis and having end walls so that a batch of the material to be dehydrated can be contained in the bottom portion of the drum and a film of the material will be carried on the inner surfaces ci the drum above the batch when the drum is rotated, a layer of desiccant surrounding the drumv and exposed to the atmosphere in the chamber, and a suction connection to said chamber.

4. Dehydrating apparatus comprising a chamber, a drum rotatable in said chamber on a horizontal axis and having end walls so that a batch of the material to be dehydrated can be contained in the bottom portion of the drum and a lm of the material will be carried on the inner surfaces of the drum above the batch when the drum is rotated, a layer of desiccant surrounding the drum yand exposed to the atmosphere in the chamber, means securing said layer on the drum to rotate therewith, and a suction connection to said chamber.

A 5. Dehydrating apparatus comprising a chamber, a drum in said chamber, said drum having end walls and trunnions secured thereto, at least one of said trunnions being hollow and serving to rounding said opening and comprising two interleaved series of concentric members oi which one a horizontal axis, means for rotating the drum,

said drum being adapted to contain in its bottom portion a batch of .the material to be dehydrated whereby upon rotation of the drum a iilm of the material will be carried on its inner surfaces above the batch, a suction connection to said chamber, and a body oi desiccant in said chamber for the sorption o! the vapor evolved from said material.

6. Dehydrating apparatus comprising a chamber, a drum in said chamber, said drum having end walls and trunnions secured thereto, at least one of said trunnions being hollow and serving to place the drum interior in communication with the chamber, means supporting the trunnions on a horizontal axis, means for rotating the drum.

-sald drum being adapted'to contain in its lbottom portion a batch oi' the material to be dehydrated whereby upon rotation oi the drum a film oi the material will be carried on its inner surfaces above the batch, a suction connection to said chamber, and baille means associated with said one of the trunnlons arranged to prevent the escape oi splash therethrough; said baille means comprising an open ended horizontally disposed body projecting inwardly of the drum from said one ofthe trunnions, said body having an annular internal enlargement intermediate its ends and radial openings communicating with said enlargement, and a baille plate supported within said enlargementin peripheraliy spaced relation to the walls` of the latter, said"V plate having an area greater than the inner openendioisald body.

'7. Dehydrating apparatus comprising a chamber adaptedto contain in the lower portion there'- e of a batch 'ofthe 'material to be dehydrated, a

Vdrum rotatable in said chamber on a horizontal axis and disposedso that its lower portion is immersed in the material-in the chamber whereby upon drum rotation a nlm oi the material will be carried on the unimmersed external surfaces in heat exchanging relation to the drum periphery, one end of the drum being open to the chamber, and a suction -connection to the other end of the drum.

` 8. Dehydrating apparatus comprising a chamis iixedand the other is-carried by the drum,-and a suction connection to the other end of said drum 9. The method of dehydrating which comprises forming a film of the material to be dehydrated, subjecting the film to reduced pressure to promote evaporation, and into a desiccant which is in heat exchanging relation with the evaporating zone, the desiccant having a suillcient heat supplying capacity so that' the iilm is maintained at a temperature above freezing.

. 10. The method of dehydrating which comprises spreading on a wall a film'of the material to be dehydrated, subjecting the iilm to reduced pressure to promote evaporation, and passing the evolved vapors into a desiccant which is in direct heat exchanging relation with said wall, the desiccant having a sufficient heat supplying capacity sothat the iilm is maintained at a temperature above freezing.`

1l. The method of dehydrating which comprises maintaining on a wall a illm continuously derived from a batch of the material to be dehydrated, subjecting the film to reduced pressure to promote evaporation, and passing the evolved oi the drum, a desiccant exposed in said drum vapors into a desiccant which is in direct heat exchanging relation with said wall, the desiccant having a suiiicient heat supplying capacity so that the iiim is maintained at a temperature above freezing.

12. The method of dehydrating which comprises ,continuously withdrawing from and returning to a batch of the material to be dehydrated a nlm of the material, subjecting the film to reduced pressure to promote evaporation until the liquid content of the `batch has been' reduced as required, and passing the evolved vapors into a desiccant which is in heat exchanging relation with the evaporating zone, the desccant having a suiilcient heat supplying capacity so that the 111m is maintained at a temperature above freezing. i

13. The method of dehydrating which comprises ,placing a batch ol.' the material to be dehydrated in a walled container, maintaining on wall portions of the container a-lm of material drawn from the batch, subjecting theiilm to reduced pressure to promote evaporation until the liquid content oi' the batch has been reduced as required, and passing the evolved vapors into a desiccant which is in direct heat exchanging relation with said Wall portions, the desiccant having a suiilcient heat supplying capacity so that the nlm is maintained at a temperature above passing the evolved vapors 

